-Bob doing homework?---No he isn’t. He is a letter.A. Does writesB. Is writes C. Doe

问题补充：

---Bob doing homework?

---No, he isn’t. He is a letter.

A. Does, writes

B. Is, writes

C. Does, writing

D. Is, writing

答案：

A. Does, writes

B. Is, writes

C. Does, writing

(答案→)D. Is, writing

解析：这是一个现在进行时的一般疑问句，所以应用is来提问,write的现在进行时是writing故选D